Saving humanity from leptospirosis
- Battling infectious disease with vaccines and diagnostic technology -

Prof.YOSHIDA

There are two kinds of Leptospira -pathogenic Leptospira, which causes illness (infectious disease) in humans and animals, and non-pathogenic Leptospira, which does not. Non-pathogenic Leptospira dwells in soil and in fresh water, such as waterways, puddles, and rivers. Pathogenic Leptospira, on the other hand, usually inhabits the kidneys of animals without causing illness to the host (i.e., rats). When excreted in the urine, it survives in soil and water. There, humans and livestock that are susceptible to it come into contact with the bacteria, and are infected through the skin or mucous membrane. The infection then causes various states of illness ranging from mild, with symptoms such as fever and muscle ache, to severe, including jaundice, kidney failure, and pulmonary hemorrhage.

Prof.YOSHIDA

Leptospira infects many animals, including pets and livestock. Mice and some other animals do not develop the disease, but become carriers, with the bacteria dwelling in their kidneys. Many pets are imported into Japan today, and they may be possibly infected with Leptospira. Imported flying squirrels have been confirmed as a source of infection, with recent cases of people being infected by them.

Prof.YOSHIDA

Leptospira dwells in soil and water, but because it shares its habitat with many other germs and molds, attempts at cultivating Leptospira usually result in a proliferation of other microorganisms that impedes the growth of Leptospira. What was needed was a culture medium that allows Leptospira to propagate while suppressing competing growth. We tested a variety of antimicrobial and antifungal agents, and after much trial and error, we developed a combination that was a good match with this objective. We named it STAFF, after the initials of the antimicrobial agents. When we sampled water from a puddle near a swimming pool and cultured it using STAFF, one of the Leptospira that emerged from the culture seemed more rugged and harder than others. Suspecting it was something that had not been seen before, we conducted tests, and were able to report discovery of a new species. We named it L. idonii, inspired by Professors Ryukichi Inada and Yutaka Ido of Kyushu University, who were the first in the world to discover that Weil's disease was an infection of Leptospira. Professor Inada already had a bacteria named after him, so we named this new strain after Professor Ido.

Prof.YOSHIDA

As part of this project, a laboratory, hamster facility, and an animal testing laboratory were installed for Leptospira research at the College of Public Health, University of the Philippines Manila. The people involved in the construction were tremendously helpful, and we are particularly indebted to the coordinators and Professor Emeritus Yasutake Yanagihara who exerted great effort to make sure that the devices and equipment delivered to the lab were the models we wanted. The process of exporting hamsters was also complicated, and we had to put in a good deal of thought to ensure that the MTA (Material Transfer Agreement) and other contract-related procedures would go smoothly. The research itself was not a problem, because we are used to the difficulties of conducting research.

Prof.YOSHIDA

Generally speaking, there are two types of diagnosis of infectious diseases-clinical diagnosis and laboratory diagnosis. Clinical diagnosis of Leptospira is difficult, so a laboratory diagnosis must be conducted in order to be certain. In order to determine if a patient has an infection, one approach is to look for pathogen-derived proteins and genes in the body of the subject suspected of being infected. Alternatively, you can study the antibodies and immune response to the pathogenic agent of the subject when our project started, testing was generally only possible at properly equipped laboratories, but that made it impossible to test outpatients, or to test at the patient's bedside or in the field. To overcome that limitation we attempted to develop simple and rapid diagnostic kits that could be used in such situations and produce quick results. Development of the antigen detection kit came to a standstill at the mass production stage, but mass production of the antibody detection kit is feasible.

Prof.YOSHIDA

A vaccine that is effective on humans already exists, and is used in Japan to inoculate farm workers and other high-risk people. It has helped to lower the number of Leptospiral infection in Japan. This SATREPS project identified serotypes endemic to the Philippines, made a vaccine from them, and confirmed its effectiveness on hamsters. The vaccine's effectiveness in livestock still needs to be confirmed before beginning human inoculations. The researchers in the Philippines will handle that process, and we are confident that they will do a good job.